1. Field of the Invention
The present invention relates to a color correcting apparatus used to correct a color to be output to an output device in response to ambient light.
2. Description of the Related Art
FIG. 1 is a schematic block diagram showing configurations of a conventional image processing device. The conventional image processing device is provided with a computer 40, a monitor 50 and a printer 60. In the conventional image processing device, the monitor 50 displays an image to be printed on the printer 60 and the printer 60 prints the image displayed on the monitor 50. Specifically, a user who operates the monitor 50 and printer 60 edits the image to be printed while watching the image being displayed on the monitor 50 and, after having checked the image displayed on the monitor 50, prints the image that has been edited on the printer 60.
Since the monitor 50 is configured to express a color using a process of additive mixture of color stimuli composed of three colors RGB (Red, Green and Blue), that is, displaying color data defining the color of the displayed image is represented by a RGB calorimetric system. On the other hand, the printer 60 is configured to express a color using a process of subtractive mixture of color stimuli composed of three colors CMY (Cyan, Magenta and Blue), that is, printing color data defining the color of the printed image is represented by a CMY colorimetric system. Therefore, conversions between the displaying color data and the printing color data are required. To achieve this, the conventional image processing device is provided with an RGB-XYZ converting section 62 to make conversions between the RGB colorimetric system and XYZ calorimetric system and with an XYZ-CMY converting section 66 to make conversions between the XYZ colorimetric system and the CMY colorimetric system.
Moreover, the color to be displayed by the monitor 50 varies depending on color reproduction characteristics of the monitor 50, while the color to be printed by the printer 60 varies depending on the color reproduction characteristics of the printer 60. The image processing device stores a monitor profile 61 obtained on the basis of the color reproduction characteristics of the monitor 50 which shows a relation between the color defined by the image color data that is input to the monitor 50 and the color that can be displayed actually by the monitor 50 and a printer profile 65 obtained on the basis of the color reproduction characteristics of the printer 60 which shows a relation between the color defined by the image color data that is input to the printer 60 and the color that can be printed actually by the printer 60. The image processing device corrects displaying color data that has been input to the monitor 50 according to the above monitor profile 61 and further printing color data which is the displaying color data that has been corrected according to the above printer profile 65 and then the printer 60 prints the color defined by the corrected printing color data.
In the image processing device, the RGB-XYZ converting section 62 converts the displaying color data (R, G and B) output from a RGB signal storing section 43 to CIE (Commission Internationale de l""echlairage) CYZ values (X, Y and Z) according to the monitor profile 61. Then an illuminant converting section 64 makes illuminant conversions of the above CIE XYZ values (X, Y and Z) and outputs the CIE XYZ values (Xxe2x80x2, Yxe2x80x2 and Zxe2x80x2) obtained by having made illuminant conversions. Moreover, the XYZ-CMY converting section 66 converts the CIE XYZ values (Xxe2x80x2, Yxe2x80x2 and Zxe2x80x2) output from the illuminant converting section 64 to printing color data (C, M and Y) according to the printer profile 65. The printer 60 prints the color based on the printing color data (C, M, Y).
The above printer profile 65 is created in the ambient light from a specified illuminant. Therefore, if the printer profile 65 has been created in the ambient light produced by using, for example, an illuminant D50, while the monitor 50 and the printer 60 are put in the ambient light produced by using any illuminant other than the illuminant D50, even if the printer profile 65 is used as it is, the printed color looks differently from its original one because the different two illuminants have been employed.
To solve this problem, in the conventional image processing device, an observation ambient illuminant information storing section 42 stores illuminant data that can correspond to a plurality of illuminants including, for example, a D50 illuminant, A illuminant, D65 illuminant, each having a different wavelength distribution, and an observation ambient illuminant information selecting section 41, in response to information, given by a user, about the illuminant producing the ambient light in which the monitor 50 and the printer 60 are put, selects best-suited illuminant data from two or more pieces of the illuminant data stored in the observation ambient illuminant information storing section 42 and outputs the selected illuminant data to the illuminant converting section 64. The illuminant converting section 64 makes illuminant conversions based on correction data calculated from the illuminant producing the ambient light in which the monitor 50 and the printer 60 are put and from the illuminant producing the ambient light used when the printer profile 65 has been created.
When the user who is putting the monitor 50 and the printer 60 in the ambient light produced by, for example, the A illuminant, inputs information requiring the A illuminant, the observation ambient illuminant information selecting section 41 selects A illuminant data XA, YA and ZA that can correspond to the information input by the user from the observation ambient illuminant information storing section 42 and outputs the selected illuminant data XA, YA and ZA to the illuminant converting section 64.
The printer 60, by using D50 illuminant data XD50, YD50, ZD50 that produces the ambient light used when the printer profile 65 is created, which is stored in a colorimetry illuminant information storing section 63, and the A illuminant data XA, YA and ZA that produces the ambient light in which the monitor 50 and the printer 60 are put, which has been fed from the observation ambient illuminant information selecting section 41, calculates correction data (Xxe2x80x2, Yxe2x80x2 and Xxe2x80x2) using the equation (1) in FIG. 15 and calibrates the printing color data based on the obtained correction data (Xxe2x80x2, Yxe2x80x2 and Xxe2x80x2).
However, the conventional image processing device has the following problem. That is, even when the printing color data is corrected by using the correction data (Xxe2x80x2, Yxe2x80x2 and Xxe2x80x2) calculated using the above equation (1) based on the illuminant producing the ambient light used when the profile 65 of the printer 60 has been created and on the illuminant producing the ambient light in which the monitor 50 and the printer 60 are actually put, since the ambient light in which the monitor 50 and the printer 60 are put contains light emitted from two or more kinds of illuminants, the color printed on the printer 60 looks differently from its original one due to an influence by light emitted from the two or more kinds of the illuminants. That is, there is the problem that the conventional image processing device cannot reproduce faithfully the original color. In addition, since the printer working as the output device is affected by the ambient light, there is the problem that the printer cannot reproduce the original color faithfully as well.
In view of the above, it is an object of the present invention to provide a color correcting apparatus capable of more faithfully reproducing an original color to be output from an output device.
According to an aspect of the present invention, there is provided a color correcting apparatus that, in order to allow an output device that outputs a first color based on first color data calibrated to output the first color in first ambient light, to output a second color substantially the same as the first color in second ambient light having wavelength distribution or chromaticity coordinates different from that of the first ambient light, corrects the first color data according to the second ambient light, the color correcting apparatus comprising: a storing section used to store two or more pieces of main component data each representing a different component of light, the main component data being combined to reproduce the second ambient light; an input section used to input two or more weighing coefficients to assign weight to each of the two or more pieces of component data when the two or more pieces of main component data are combined; and a correcting section used to correct the first color data based on correction parameters obtained using the two or more pieces of component data stored in the storing section and using the two or more weighing coefficients input through the input section.
It is preferable that correction parameters providing achromatic color displaying are employed for the color correction in color display based on achromatic color data using the correction parameters in the second ambient light. It is further preferable that the achromatic color data is chromatic color data having a hue.
It is preferable that the main component is a representative light component obtained by analysis and synthesis of two or more kinds of ambient light each being different from each other. It is further preferable that the main component data represents wavelength distribution of light obtained by the synthesis of the two or more kinds of ambient light.
It is preferable that the color correcting apparatus further comprises a displaying section used to display a color based on the color data corrected by the correcting section in order to obtain the correction parameters required for correcting the second ambient light. It is further preferable that the displaying section is a section on which a color is displayed by either a RGB (Red, Green and Blue) colorimetric system or a CMY (Cyan, Magenta and Yellow) colorimetric system. It is still further preferable that the displaying section in which a color is displayed by the RGB calorimetric system is a monitor and the displaying section in which the color is displayed by the CMY calorimetric system is a printer.
It is preferable that the displaying section is either the displaying section using a process of additive mixture of color stimuli or the displaying section using a process of subtractive mixture of color stimuli.
It is preferable that the output device is a displaying section on which a color is displayed by either the RGB calorimetric system or the CMY colorimetric system. It is further preferable that the displaying section in which a color is displayed by the RGB calorimetric system is a monitor and the displaying section in which the color is displayed by the CMY colorimetric system is a printer.
It is preferable that the color correcting apparatus further comprises a calibrating section used to calibrate a color based on the color data corrected by the correcting section in order to obtain the correction parameters required for correcting the second ambient light.
It is preferable that the output device is the output device using a process of additive mixture of color stimuli or the output device using a process of subtractive mixture of color stimuli.